1. Field of the Invention
The present invention relates to a valve timing control device altering timing for the closing and opening of an exhaust valve or intake valve of an internal-combustion engine (hereafter, referred as an engine) with reference to any operating conditions.
2. Description of the Prior Art
Conventional valve timing control devices shown in FIG. 1 to FIG. 5 for example are known. FIG. 1 is a lateral cross sectional view of an internal construction of a conventional vane-equipped valve timing control device. FIG. 2 is a longitudinal cross sectional view taken along lines Axe2x80x94A of FIG. 1. FIG. 3 is a longitudinal cross sectional view of a conventional locking/unlocking mechanism shown in FIG. 2. FIG. 4 is an enlarged perspective view of an important part of a locking/unlocking mechanism of the conventional valve timing control device shown in FIG. 1. FIG. 5 is a graph of a relationship between an operational stroke of a locking member of the conventional locking mechanism shown in FIG. 2 and FIG. 3 and a hydraulic pressure exerted on the locking member. Moreover, in FIG. 2, right side is defined as forward and left side is defined as backward. In FIG. 3 and FIG. 4, lower side is defined as forward and upper side is defined as backward.
In the drawings, a reference numeral 1 denotes a first rotor, which is coupled to a crankshaft (not shown) as an output shaft of the engine by way of chains (not shown), belts (not shown) and so on and is rotatable in synchronization with the crankshaft (not shown). The first rotor 1, a sprocket 2, a case 3 and a cover 4 are fixed integrally using a threaded member 5 such as bolts. The sprocket 2 is rotated integrally with the crankshaft (not shown). The case 3 has a plurality of shoes 3a projected inwardly from an inner periphery of the case 3 to constitute a plurality of hydraulic chambers. The hydraulic chambers are covered with the cover 4.
A rotor (second rotor) 6 is rotated relative to the first rotor 1 and is disposed in the case 3. The rotor 6 is integrally fixed on a camshaft 7, which relates to timing for the closing and opening of intake or exhaust valve, using a threaded member 8 such as bolts. The rotor 6 has a plurality of vanes 6a each partitioning the hydraulic chambers, which are constituted by the shoes 3a of the case 3, into an advance side hydraulic chamber 9 and a retardation side hydraulic chamber 10. A first oil path (hydraulic chamber supply path) 11 and a second oil path (hydraulic chamber supply path) 12 are arranged in the camshaft 7. The first oil path 11 supplies a hydraulic pressure to the advance side hydraulic chamber 9 and discharges the hydraulic pressure therefrom. The second oil path 12 supplies a hydraulic pressure to the retardation side hydraulic chamber 10 and discharges the hydraulic pressure therefrom.
Seal means 13 are disposed at front ends of the shoes 3a of the case 3 and at front ends of the vanes 6a of the rotor, respectively. Each of the seal means 13 prevents an oil leak from a boundary between the advance side hydraulic chamber 9 and the retardation side hydraulic chamber 10. The seal means 13 includes a seal member 13a sliding over an inner wall of the advance side hydraulic chamber 9 or the retardation side hydraulic chamber 10 and a leaf spring 13b pressing the seal member 13a against the inner wall thereof.
An accommodation hole 14 accommodating a locking pin described later is arranged at one of the vanes 6a of the rotor 6 as the second rotor. The locking pin (locking member, lockingmechanism) 15, which controls relative rotation of the first rotor 1 and the second rotor and is defined as a straight pin having a cylindrical shape, is disposed in the accommodation hole 14. The locking pin 15 prevents the occurrence of beat noise (abnormal noise). The second rotor 6 vibrates in rotational directions due to loads of cams (not shown) integrally fixed to the camshaft 7 when the engine is started in a state of hydraulic pressure-free in the valve timing control device. The rotor 6 attaches repeatedly to or detaches from the first rotor 1 due to the vibration. Therefore, the beat noise occurs due to the repetition. the locking pin 15 is pressed against the first rotor 1 at all times using a biasing means (locking mechanism) 16 such as coil springs disposed between a rear wall of the accommodation hole 14 and the locking pin 15 and engages in an engagement hole described later. A discharge hole (unlocking mechanism) 17, which discharges a backward pressure exerted on the back section of the locking pin 15 to outside of the device, is formed in the accommodation hole 14.
On the other hand, an engagement hole 18 is formed at a position of the sprocket 2 defined as the first rotor 1. The position of the sprocket 2 allows the fit of the locking pin 15 into the engagement hole 18 when the rotor 6 defined as the second rotor locates at the most retarded position with respect to the first rotor 1.
A check valve (unlocking mechanism) 19 is arranged at the vane 6a having the accommodation hole 14. The check valve 19 selects the higher pressure of the two different pressures in the advance and retardation side hydraulic chambers 9 and 10, and supplies the selected pressure to the engagement hole 18 engaged with the locking pin 15 to unlock the engagement (hereafter, referred as locking relation). The check valve 19 communicates to the engagement hole 18 by way of a first unlocking hydraulic pressure supply path (unlocking mechanism) 20 formed in the vane 6a of the rotor 6, a second unlocking hydraulic pressure supply path (unlocking mechanism) 21 formed in the sprocket 2. The check valve 19 communicates to the advance side hydraulic chamber (unlocking mechanism) 9 by way of an advance side partitioned pressure path (unlocking mechanism) 22. The check valve communicates to the retardation side hydraulic pressure chamber 10 by way of a retardation side partitioned pressure path (unlocking mechanism) 23.
An unlocking operation will be explained hereafter.
On unlocking the locking relation, a hydraulic pressure derived from an oil pump (not shown) passes through the advance side hydraulic chamber 9 or the retardation side hydraulic chamber 10. The hydraulic pressure is then supplied to the engagement hole 18 through the check valve 19, the first and second unlocking partitioned pressure paths 20 and 21. In the engagement hole 18, an unlocking hydraulic pressure is supplied to a boundary between the inner wall of the engagement hole 18 and an outer wall of the locking pin 15 and presses the locking pin 15 against a biasing force of the biasing means 16. In this way, the locking pin 15 is moved back the deep of the accommodation hole 14 and is released from the engagement hole 18. At this time, the backward pressure of the locking pin 15 is discharged from the accommodation hole 14 through the discharge hole 17 to outside of the valve timing control device. When a front end of the locking pin 15 is released from the engagement hole 18 and the whole is come back to the accommodation hole 14, it is possible to unlock the locking relation to allow a free rotation of the first and second rotors.
Moreover, since a pressure-exerted area, on which a hydraulic pressure is exerted, of the locking pin 15 is constant over a period of time during the switching from a locked state due to the locking pin 15 to an unlocked state, a discharge speed of the backward pressure becomes constant. The operational stroke of the locking pin 15 is determined depending on the biasing force of the biasing means 16 and the hydraulic pressure to establish the one-on-one relationship between the operational stroke of the locking pin 15 and an applied hydraulic pressure as illustrated in FIG. 5. A nun locking hydraulic pressure is the same as a hydraulic pressure (unlocking-keeping hydraulic pressure) keeping the unlocking hydraulic pressure.
Incidentally, in a state of stopping the engine, oil in the advance side hydraulic chamber 9 and the retardation side hydraulic chamber 10 comes down to an oil pan (not shown) by way of the first oil path 11, the second oil path 12 and soon. It results in remaining air in the respective hydraulic chambers and pipes such as oil paths. In such a state, on restarting the engine, a hydraulic pressure rises due to the oil pump (not shown) and simultaneously the air remained in the pipes is pressed at a dash to the valve timing control device. As a result, air-mixed oil in the valve timing control device is supplied to the engagement hole 18 to exert on the locking pin 15.
The conventional valve timing control device is however configured as described above. When air-mixed oil exerts on the locking pin 15 to unlock the locking relation on starting the engine, the hydraulic pressure in the advance side hydraulic chamber 9 and the retardation side hydraulic chamber 10 can hardly absorb the loads of the cams. Since the second rotor therefore attaches repeatedly to or detaches from the first rotor 1, it is difficult to prevent the occurrence of the beat noise (abnormal noise) due to the repetition.
Moreover, another conventional valve timing control devices disclosed in JP-A-159519/1998, for example, are also known. It is an object of the conventional device to provide a device having no problems that the air-mixed oil unlocks accidentally the locking relation of a tier-equipped pin and an engagement hole before a hydraulic pressure adequately rises on starting the engine and so on. The device is equipped with an unlocking hydraulic chamber formed between a shoulder section of the tier-equipped pin and an accommodation hole, and is equipped with a communication path communicating between the unlocking hydraulic chamber and a retardation side hydraulic chamber. The device is also equipped with a pressure release path communicating between a discharge hole formed in the accommodation hole, which accommodates the tier-equipped pin, and the unlocking hydraulic chamber in order to discharge only the air to outside.
However, the conventional valve timing control device is so configured as to allow oil and air (pressurized fluid), which reach the pressure release path, to pass through the unlocking hydraulic chamber. Here, when the air-mixed oil in trace amounts exerts on the shoulder section of the tier-equipped pin, the pressure release path is sealed with oily components of the air-mixed oil and accordingly the discharge of air is hardly performed. Therefore, there is a possibility that the locking relation of the tier-equipped pin is unlocked before the hydraulic pressure adequately rises and the conventional device cannot solve the problems above.
On the other hand, Japanese Patent No. 3,085,219 discloses a valve timing control device having a structure allowing to block a communication path with a tier-equipped pin, the communication path communicating between an unlocking hydraulic chamber and a retardation side hydraulic chamber on unlocking a locking relation. With the conventional valve timing control device, an advance side hydraulic pressure is applied to a boundary between a front end of the tier-equipped pin and an engagement hole and accordingly it is possible to unlock the locking relation. When the locking relation is unlocked at one time and the tier-equipped pin is moved back, the communication path is opened. In this way, it is possible to keep the unlocked state using not only the advance side hydraulic pressure but also a retardation side hydraulic pressure.
The conventional valve timing control device is however configured as described above. When the locking relation is unlocked due to the application of the advance side hydraulic pressure and the retardation side hydraulic chamber communicates to the unlocking hydraulic chamber by way of the communication path, the unlocking hydraulic chamber is not yet filled with oil at this time. Therefore, when the application of the advance side hydraulic pressure is switched to the application of the retardation side hydraulic pressure, the hydraulic pressure does not exert adequately on the tier-equipped pin. Thus, there is a possibility that the tier-equipped pin moves forward due to a biasing force of a biasing means biasing the tier-equipped pin toward an engagement hole at all times and that the tier-equipped pin engages in the engagement hole.
Any devices disclosed in the gazettes above are predicated on using the tier-equipped pin and it is difficult to use a straight pin usable in the conventional valve timing control device shown in FIG. 1 to FIG. 5. The tier-equipped pin and a sliding hole allowing the insertion of the locking pin are produced in more complicated processes as compared with the straight pin. It is desirable that the valve timing control device has general versatility allowing the use of any kinds of locking pins.
Accordingly, it is an object of the present invention to provide a valve timing control device allowing the use of any kinds of locking pins, and preventing the occurrence of beat noise (abnormal noise) when air-mixed oil unlocks a locking relation on starting the engine.
In order to achieve the object of the present invention, we provide a valve timing control device, comprising: a first rotor rotatable in synchronization with a crank shaft of an internal-combustion engine and having a plurality of shoes formed at an inner periphery of the first rotor; a second rotor fixed at an end of an intake or exhaust camshaft of the internal-combustion engine, arranged in the first rotor, rotatable relative to the first rotor, and having a plurality of vanes formed at an outer periphery of the second rotor; an advance side hydraulic chamber and a retardation side hydraulic chamber formed between the vanes of the second rotor and the shoes of the first rotor; a locking member locking either of the first and second rotors with respect to the remainder at a required angle; an accommodation hole arranged at either of the first and second rotors, accommodating the locking member and a biasing means biasing the locking member, and having a discharge hole discharging a backward pressure exerted on aback section of the locking member to outside; an engagement hole arranged at the remainder, allowing the insertion of the locking member; an unlocking hydraulic chamber; and an unlocking hydraulic pressure supply path supplying a hydraulic pressure to the unlocking hydraulic chamber; wherein at least one of the advance and retardation side hydraulic chambers is equipped with a purge path communicating to the atmosphere. In this way, air or air-mixed oil having the potential for being used in first motion of the unlocking operation on starting the engine can be discharged positively to outside. Therefore, it is possible to unlock the locking relation after the applied hydraulic pressure reaches a level of allowing the control of the valve timing control device and to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, it may further comprises a check valve having an advance side partitioned pressure path communicating the advance side hydraulic chamber and having a retardation side partitioned pressure path communicating the retardation side hydraulic chamber, the check valve selecting the higher pressure of the two different pressures in the advance and retardation side hydraulic chambers to supply the selected pressure to the unlocking hydraulic pressure supply path, wherein at least one of the advance side hydraulic chamber, the retardation side hydraulic chamber, the advance side partitioned pressure path and the retardation side partitioned pressure path is equipped with a purge path communicating to the atmosphere. In this way, air or air-mixed oil used in first motion of the unlocking operation on starting the engine can be discharged positively to outside. It is unnecessary to devote all pressure produced in the first motion to the unlocking operation. Therefore, it is possible to unlock the locking relation after the applied hydraulic pressure reaches a level of allowing the control of the valve timing control device and to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, the purge path may be connected to a backward pressurized section in the accommodation hole, the backward pressurized section functioning as a backward pressurized chamber for the locking member. In this way, a hydraulic pressure produced due to air-mixed oil, which is supplied to the backward pressurized section in the accommodation hole by way of the purge path, competes against an unlocking hydraulic pressure supplied to the engagement hole by way of the unlocking hydraulic pressure supply path. Therefore, it is possible to delay the unlocking operation and accordingly prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, a drain path communicating between the purge path and the atmosphere may be connected to the backward pressurized section in the accommodation hole, the backward pressurized section functioning as a backward pressurized chamber for the locking member. In this way, it is possible to discharge quickly the air-mixed oil due to the drain path with the locking relation being unlocked.
With the above arrangement, the purge path may communicate at least one of the retardation side hydraulic chamber, the advance side hydraulic chamber, the retardation side partitioned pressure path or the advance side partitioned pressure path to the atmosphere. In this way, air-mixed oil is supplied to the accommodation hole by way of at least one of the retardation side hydraulic chamber, the advance side hydraulic chamber, the retardation side partitioned pressure path or the advance side partitioned pressure path, and the purge path to produce a hydraulic pressure. The hydraulic pressure competes against an unlocking hydraulic pressure supplied to the engagement hole by way of the unlocking hydraulic pressure supply path. Therefore, it is possible to delay the unlocking operation at a low hydraulic pressure on starting the engine and so on.
With the above arrangement, the purge path may be connected to the backward pressurized section in the accommodation hole so that the purge path is blocked with the locking member in a state of unlocking the locking relation. In this way, when the locking relation is unlocked after the air-mixed oil is discharged to outside, the supply of a hydraulic pressure derived from the purge path to the accommodation hole is cutoff. Therefore, it is possible to prevent the residual pressure from being produced in the accommodation hole.
With the above arrangement, the purge path may be connected to the backward pressurized section in the accommodation hole so that the purge path is blocked with the locking member over a period of time during from the state of starting a locking operation to the state of moving the locking member by a required stroke. In this way, the supply of a hydraulic pressure derived from the purge path to the accommodation hole is cut off over the period of time above. Therefore, it is possible to prevent the residual pressure from being produced in the accommodation hole.
With the above arrangement, at least one part of the purge path, the discharge hole, the drain path, the retardation side partitioned pressure path of the check valve or the unlocking hydraulic pressure supply path may be equipped with a throttle for narrowing an opening area of them. In this way, when the purge path is equipped with the throttle, it is possible to increase resistance produced in the purge path and to restrict to pass oil, which has incompressibility and high-viscosity, in the air-mixed oil through the purge path. At the same time, it is possible to pass selectively air, which has compressibility and low-viscosity, through the purge path. When the discharge hole or the drain path is equipped with the throttle, it is possible to restrict to discharge the oil. In case a malfunction occurs mechanically in the locking pin in the locked state to remain the purge path to be opened for any reason, it is possible to reduce the amount of oil consumed repeatedly to a minimum level. Therefore, it is possible to avoid engine failure from causing owing to lack of lubricant. When the retardation side partitioned pressure path or the unlocking hydraulic pressure supply path includes the throttle, it is possible to direct the amount of air-mixed oil, which is more than that of the retardation side partitioned pressure path or the unlocking hydraulic pressure supply path, toward the purge path.
With the above arrangement, an opening area of the purge path may be set to be narrower than that of a pressurized chamber supply path supplying a hydraulic pressure to the advance side hydraulic chamber or the retardation side hydraulic chamber. In this way, it is possible to keep a hydraulic pressure in the advance side hydraulic chamber and the retardation side hydraulic chamber.
With the above arrangement, the opening area of the purge path may be set to be equal to or be larger than that of the discharge hole or the drain path. In this way, it is possible to produce a residual pressure in a direction of delaying the unlocking operation on starting the engine. Further, it is possible to set the unlocking hydraulic pressure to become higher than the unlocking-keeping hydraulic pressure and to prevent the locking relation from being unlocked accidentally on starting the engine. As a result, it is possible to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, the opening area of the purge path may be set to be larger than that of any one of the advance side partitioned pressure path, the retardation side partitioned pressure path and the unlocking hydraulic pressure supply path. In this way, it is possible to direct air-mixed oil toward the purge path having higher priority than the unlocking hydraulic pressure supply path. It is possible to restrict to pass oil, which has incompressibility and high-viscosity, in the air-mixed oil through the purge path and to pass selectively air, which has compressibility and low-viscosity, through the purge path. As a result, it is possible to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, opening areas of the pressurized chamber supply path, the purge path, the drain path and the unlocking hydraulic pressure supply path may be so set as to satisfy the following inequality: the pressurized chamber supply pathxe2x89xa7the purge pathxe2x89xa7the drain pathxe2x89xa7the unlocking hydraulic pressure supply path. In this way, it is possible to direct air-mixed oil toward the purge path having higher priority than the unlocking hydraulic pressure supply path. It is possible to restrict to pass oil, which has incompressibility and high-viscosity, in the air-mixed oil through the purge path and to pass selectively air, which has compressibility and low-viscosity, through the purge path.
With the above arrangement, the opening areas may be so set as to produce a pressure different between an unlocking hydraulic pressure and an unlocking-keeping hydraulic pressure. In this way, it is possible to set the unlocking hydraulic pressure to become higher than the unlocking-keeping hydraulic pressure and to prevent the locking relation from being unlocked accidentally on starting the engine. As a result, it is possible to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, a biasing force of a biasing means may be so set as to produce a pressure different between an unlocking hydraulic pressure and an unlocking-keeping hydraulic pressure. In this way, it is possible to set the unlocking hydraulic pressure to become higher than the unlocking-keeping hydraulic pressure and to prevent the locking relation from being unlocked accidentally on starting the engine. As a result, it is possible to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, a pressure-exerted area of a tier-equipped locking member is so set as to produce a pressure different between an unlocking hydraulic pressure and an unlocking-keeping hydraulic pressure. In this way, it is possible to set the unlocking hydraulic pressure to become higher than the unlocking-keeping hydraulic pressure and to prevent the locking relation from being unlocked accidentally on starting the engine. As a result, it is possible to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, the unlocking hydraulic pressure of the locking member using either of the retardation side hydraulic pressure and the advance side hydraulic pressure may be set to be larger than a maximum hydraulic pressure in the engine or a relief valve hydraulic pressure. In this way, however a hydraulic pressure, which is supplied to either of the retardation side hydraulic chamber and the advance side hydraulic chamber, rises on starting the engine, the locking relation of both rotors cannot be unlocked due to the risen hydraulic pressure. Accordingly, it is possible to prevent the locking relation from being unlocked accidentally on starting the engine and to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, when the first and second rotors are locked, a hydraulic chamber allowing entry of a hydraulic pressure on starting the engine may communicate to an unlocking hydraulic chamber and the backward pressurized section in the accommodation hole, respectively. In this way, an unlocking hydraulic pressure and a backward pressure competing against the unlocking hydraulic pressure are exerted on the locking member in both directions. Therefore, it is possible to prevent the locking relation from being unlocked due to a hydraulic pressure of the hydraulic chamber allowing entry of hydraulic pressure on starting the engine. Moreover, it is possible to prevent the locking relation from being unlocked accidentally on starting the engine and to prevent the occurrence of the beat noise (abnormal noise) with reliability.
With the above arrangement, the locking member may be released from the engagement hole due to a hydraulic pressure of a hydraulic chamber opposite to the hydraulic chamber allowing the entry of hydraulic pressure on starting the engine, and wherein when the first and second rotors are unlocked, the purge path defined between the hydraulic chamber allowing the entry of hydraulic pressure on starting the engine and the backward pressurized section in the accommodation hole may be blocked with the locking member. In this way, it is possible to allow the unlocking operation only when a hydraulic pressure of a hydraulic chamber opposite to the hydraulic chamber allowing the entry of hydraulic pressure on starting the engine exerts on the locking member. When the locking relation is unlocked at one time, it is possible to ensure the unlocked state due to either of the hydraulic pressures.
With the above arrangement, the hydraulic chamber allowing the entry of hydraulic pressure on starting the engine may be the retardation side hydraulic chamber. In this way, it is possible to produce the residual pressure exerted on the locking member in a direction of locking the locking member due to the hydraulic pressure of the retardation side hydraulic chamber allowing the entry of hydraulic pressure. Accordingly, it is possible to prevent the locking relation from being unlocked due to the retardation side hydraulic pressure with reliability.